The trend in gas turbine engines is to improve engine efficiencies by increasing the OPR. This results in a relatively smaller core, and a higher bypass ratio. As OPR increases, the exit temperature of the high pressure compressor (HPC) correspondingly increases. Typically, in some known engines, areas of the engine that can limit OPR include temperatures that occur in spacer arm materials, rim and attachment materials, the cone shaft, and in the compressor-turbine (C-T) shaft. Known gas turbine engines also may include a secondary flow system that plumbs hot compressor air down the HPC cone shaft and along the C-T shaft. However, temperatures at the aft end of the compressor may be close to the compressor exit temperature. And, future engines being considered have compressor exit temperatures that may exceed material limits.
In some known systems, cooling air in the aft end is cooled to generate cooled cooling air (CCA) and a secondary flow system, and there have been approaches for CCA in which the drive cone and C-T shaft are exposed to CCA. However, CCA systems typically focus on managing temperatures within the hot section of the engine (NGV's, high-pressure turbines (HPTs), other turbines, turbine casings, etc.). And, secondary flow circuits typically transfer flow between the gas path and the bores and the flow is typically taken in only one direction.
As a result there is a need to thermally manage the aft end of the HPC to maintain metal temperatures within the temperature range for which materials are capable. By having an effective thermal management system, a higher OPR cycle can be enabled resulting in improved specific fuel consumption (SFC) and less fuel burn per aircraft mission.